IELTS Academic Reading passage: Microplastics in the Global Food Chain

Microplastics in the Global Food Chain

Microplastics are defined as plastic particles smaller than five millimetres in their longest dimension. They enter the environment through multiple pathways: the degradation of larger plastic items exposed to sunlight and mechanical stress; the release of synthetic fibres during the washing of clothes made from polyester, nylon, and acrylic; the breakdown of plastic packaging; and the direct manufacture of microbeads formerly incorporated into cosmetics. Although microbeads have been banned in several countries, remaining sources continue to release microplastics into waterways, soils, and the atmosphere at significant rates.

Once in the environment, microplastics are ingested by a wide range of organisms, from zooplankton, the microscopic animals at the base of many aquatic food chains, to fish, seabirds, and marine mammals. When zooplankton consume microplastics, they may experience satiation, a false sense of fullness, that reduces their actual food intake and impairs their reproduction and growth. This disruption at the base of the food chain can have cascading effects on species further up, including commercially important fish.

As organisms at lower trophic levels consume microplastics and are themselves consumed by larger predators, the concentration of microplastic particles can increase at each level in a process known as biomagnification. This means that top predators, including humans, may be exposed to significantly higher concentrations of microplastics than the ambient environment would suggest. However, the evidence for classical biomagnification of microplastics specifically remains disputed among scientists.

Studies have detected microplastics in bottled water, tap water, sea salt, honey, beer, and commercially sold seafood. Research conducted in 2018 estimated that the average person may ingest approximately 50,000 microplastic particles per year through food and water alone, with additional exposure occurring through inhalation. Plastic particles have also been found in human blood, lung tissue, and placental tissue, indicating that they can cross biological barriers and accumulate in the body.

The health implications of microplastic ingestion remain a subject of active research. Laboratory studies on animals have linked exposure to chemicals associated with plastics, including phthalates and bisphenol A, to hormonal disruption and cellular damage. However, establishing direct causal links between microplastic exposure and human health outcomes is complicated by difficulties in isolating plastic-related effects. The World Health Organisation concluded in 2019 that risks from microplastics in drinking water are currently low, while acknowledging significant uncertainty.

Policy responses have been varied. Some countries have implemented bans on single-use plastics, while others have set recycling targets. Critics argue that these measures are insufficient given the scale of plastic production, and that more radical systemic changes are required to meaningfully reduce microplastic contamination of the environment.